Alloy



Patented Feb, 10, 1942 ALLOY Edmund A. Anderson and Gerald Edmunds,Palmerton, Pa., assignors to The New Jersey Zinc Company, New York, N.Y., a corporation of New Jersey No Drawing.

Original application January 16,

1940, Serial No. 314,086. Divided and this ap-' plication July 18, 1941,Serial No. 402,994

3 Claims.

This invention relates to zinc base alloys and provides new alloyscontaining zinc, manganese and aluminum (and, preferably, also iron) andhaving superior mechanical properties. The alloys of our invention havean appearance similar to that of white metal alloys.

This application is a division of our co-pending application Serial No.314,086, filed January 16, 1940.

We have discovered new zinc alloys containing certain proportions ofmanganese and aluminum with or without a small proportion of iron which,as cast, have an impact strength of about one foot-pound per one-quartersquare inch crosssection or more, a tensile strength of about 60,000pounds per square inch or higher, and high creep resistance. They may beformed into intricate shapes of accurate configuration by die-casting,and are also amenable to casting by other methods.

All percentages and parts given hereinafter are by weight, and on thisbasis the alloys of our invention contain about 0.02 part to about 5parts aluminum, about 33.3 parts to about 48.5 parts manganese, about66.7 parts to about 51.5 parts zinc, and may in addition contain up to 6parts iron.

If the foregoing alloy is so constituted that it consists of about 0.02part to about 5 parts aluminum, about 38 parts to about 48.5 partsmanganese and about 62 to about 51.5 parts zinc, with or without a smallproportion of iron, say less than 6 parts, it will. have as cast atensile strength of at least 60,000 pounds per square inch and an impactstrength of at least two foot-pounds per one-quarter inch squaresection. If the alloy consists of about 0.02 part to about 2 partsaluminum, about 43 parts to 48.5 parts manganese.

and about 57 to about 51.5 parts zinc, with or without iron up to 6parts, it will have as cast an impact strength of at least fourfoot-pounds per one-quarter inch square section.

In the manufacture of the alloys of our invention, it is not essentialin all cases to employ high grade manganese for the impurities that mayoccur in the ordinary commercial grades of manganese may be included inoir alloys in some cases without too serious effect upon the propertiesthereof. Manganese suitable for use in the practice of our invention maycontain minor proportions of silicon, phosphorus, carbon, nitrogen, andother impurities. We prefer, however, to use manganese of highpurity-because impurities in the manganese may degrade the mechanicalproperties of the alloy, and, in particular, cause the presence of hardparticles that may interfere with machining and bufling.

The alloys of our invention are relatively hard, having ,a Brinellhardness in the neighborhood of to 165.

Alloys of our invention are not subject to the temperature embrittlementencountered in many zinc alloys at very low temperatures and have highcreep resistance, considerably better than heretofore customary zincbase die-casting alloys. The modulus of elasticity of the alloysof ourinvention is also greater than that of heretofore customary zinc basedie-casting alloys and is in the neighborhood of 14,000,000 pounds persquare inch.

The alloys of our invention possess apparent rigidity or stiffness to adegree greater than that of any other zinc alloys of reasonableductility known to us, and all of the alloys of our invention aremachinable. Further, these alloys manifest good resistance toatmospheric corrosion and inwater immersion tests showed a corrosionresistance roughly comparable to that of the'zinc base die-castingalloys, Nos. XXI, XXIII, and IQIV of A. S. T. M. tentativespecifications B86- 38T, 1938.

As indicated hereinbefore, aluminum is an essential ingredient in thealloys of our invention.

The aluminum not only improves the casting characteristics of thealloys, but also tends to suppress oxidation of the surfaces of the hotcasting so that the alloys of our invention maybe cooled in air withoutserious discoloration. Moreover, the presence of the aluminum in thealloy within the range specified, i. e., 0.02% to about 5%, reducesdross formation on the molten alloy during casting operations and tendsto impart an attractive silvery appearance to the casting. When aluminumis not present, a tenacious brown film tends to form on the molten'alloy, interfering with p ouring and making difficult the production ofa casting having a smooth surface. The resulting casting is also'unsuitable in that it acquires a brownish discoloration on the surface.However, an aluminum content of more than 5% cannot be tolerated becauseof the deleterious effect thereof upon the mechanical properties of thealloys. In case the aluminum content exceeds 2%, the tolerance forimpurities is limited.

The inclusion of up to 6% iron in the alloys ofour invention isdesirable. iron of the particular alloy depends upon its manganese andimpurity .contents and is greater 55 for some compositions.

The tolerance for the form of unalloyed metals or alloys of these witheach other. We prefer to melt the alloys in a crucible substantiallynon-reactive to the alloys. Clay-silicon carbide and cast iron crucibleshave been satisfactory. It is helpful in many cases to protect thesurface of the molten alloy with a non-reactive gas, e. g., hydrogen.

As indicated hereinbefore, the alloys of our invention can be die-castand because of their greater strength and hardness offer certainadvantages over heretofore customary zinc diecasing alloys. Certainalloys of our invention have been gravity cast in permanent metal mouldsand also gravity cast in sand moulds. Although some difierences inproperties of the alloys of our invention are induced by the method ofcasting, the alloys of our invention in general exhibit superiorproperties as compared to heretofore customary zinc alloys, irrespectiveof the particular method of casting.

We claim:

1. An alloy consisting of about 0.02 part to about 5 parts aluminum andabout 33.3 parts to 48.5 parts manganese and about 66.7 to about 51.5parts zinc.

2. An alloy having as cast an impact strength of at least about 2foot-pounds per A inch square section and a tensile strength of at leastabout 60,000 lbs. per square inch and consisting of about 0.02 part toabout 5 parts aluminum, manganese in proportions ranging from about 38parts to about 48.5 parts, and about 62 to about 51.5 parts zinc.

3. An alloy having as cast an impact strength of at least 4 foot-poundsper inch square section and consisting of about 0.02 part to about 2parts aluminum, about 43 parts to about 48.5 parts manganese and about57 to about 51.5 parts zinc.

EDMUND A. ANDERSON. GERALD EDMUNDS.

